Plastering is one of the oldest crafts in the building trades. Plastering remains popular due to the durability and relatively low cost of materials. Plasterers apply plaster to interior walls and ceilings to form fire-resistant and relatively soundproof surfaces. A plaster veneer may also be applied over drywall to create smooth or textured abrasion-resistant finishes. In addition, prefabricated exterior insulation systems may be applied over existing walls. Stucco masons apply durable plasters, such as polymer-based acrylic finishes and stucco, to exterior surfaces.
Plasterers can plaster either solid surfaces, such as concrete block, or supportive wire mesh called lath. When plastering metal-mesh lath foundations, plasterers apply a preparatory, or “scratch coat” with a trowel. The scratch coat is spread into and over the lath. Before the plaster sets, plasterers scratch the surface of the scratch coat with a rake-like tool to produce ridges, so that the subsequent brown coat will bond tightly. The brown coat may then be applied. Later, the finish, or white coat is applied onto the scratch coat. Similar steps are followed when applying stucco and other materials to the lath.
The structure of the lath is what provides mechanical integrity to an overall masonry system. When mortar fills the small voids, it is called keying. Expanded lath has applications in the installation or manufacture of tile, countertops, shower surrounds, manufactured stone and natural stone veneers, brick, concrete stairs, and other masonry systems.
A commonly used lath material is metal lath. Metal lath is typically manufactured from steel sheets that are slit and expanded to form diamond shaped openings. The openings provide keys for securing plaster or a cementitious substrate such as stucco to the lath material, whether the base material is troweled on or mechanically applied. In addition, the shape of the orifice is designed to promote keying of the cementitious material to the lath.
If the metallic lath is weakened by corrosion, cracks tend to result in the cementatious material. In some cases, crack propagation may result in cracking of the stone, plaster, or stucco, which may be visible, unattractive, and unstable. Galvanized metal lath was introduced in an attempt to prolong the life of the metal lath in a corrosive cementitious environment. The corrosive effects resulted from moisture and alkalinity due to the lime content in cement based mortar. However, galvanized metal lath still has a tendency to rust and deteriorate, thus providing a substrate that is prone to fail.
Efforts have been made to develop non-metallic reinforcement systems and to use those systems for both structural and crack resistant properties. Fiberglass and plastic lathing systems have been introduced in the industry. The fiberglass and plastic lath have advantages, such as ease of handling, i.e., fiberglass and plastic lath come in rolls and are lighter than traditional metal lath, and the fiberglass and plastic lath does not rust. Additionally, plastic or fiberglass lath is easier to use because it may be cut with a sharp blade of a utility knife. Plastic lath is mainly used in the plaster and floor overlay applications. Examples of fiberglass and plastic lath include products sold under the trademark Ultra-lath®. Permalath® and Fiberlath are other fiberglass products used in structural reinforcement.
Fiberglass mesh, while not usually subject to corrosion, can be affected by the corrosive nature of cementitious material. For that reason, fiberglass mesh used as lath is usually coated with an alkali resistant material like zirconium dioxide to protect the fiberglass from the corrosive nature of many cementitious materials. The oxidation of fiberglass has been proven to not create structural degradation or mechanical weakening, unlike metallic materials embodied in cementitious material.
When constructing a wall system, studs are typically used to hold up the wall and sheathing is applied to the studs as a covering. To protect the sheathing, which is usually untreated wood, a vapor or water barrier is placed on the sheathing to stop moisture from reaching the untreated wood. Water/vapor barriers are usually tar paper, felt paper, plastic and more recently Tyvek® building wrap. If the water proofing layer is perforated, then the water barrier is compromised. Once water has penetrated the water barrier any untreated wood is susceptible to damage, such as dry rot and mold. One opportunity for perforating the water proofing layer is when structural support systems are applied over the water barrier and fastened to the substrate. In the fastening process the fasteners penetrate the water barrier, thus compromising the barrier and allowing a pathway for moisture to come in to contact with the wood sheathing. In the process of installing the lath as many as 200 penetrations in an 18 sq. ft. area may be found, thus causing irreparable damage to the water barrier and to the structural framing.
Additionally, when fasteners are in contact with moisture for prolonged period of time, such as water saturated wood, the galvanized anchors undergo corrosive fatigue and lose their structural integrity as a valid anchor or a mechanical fastener.
Therefore, it is desirable to provide an improved structural reinforcement system that provides integral waterproof sealing capabilities for anchor penetration through the water/vapor barrier.
It is further desirable to provide a structural reinforcement system that reduces the impact of the mechanical anchoring device during fastener application to prevent damage to the surface of the structural reinforcement system when secured to the anchoring point to prevent corrosion.
It is a further desirable to provide a structural reinforcement system that has adjustable nailing/mechanical fastening guides.
It is additionally desirable provide a structural reinforcement system that embodies a directional water drainage system in the structural reinforcement system. It is further desirable to provide an improved structural reinforcement system that has improved keying over conventional fiberglass lath.
It is additionally desirable to provide an improved flexible lath that has a profile that is three dimensionally uniform to provide improved keying of mortar and to facilitate a consistent and repeatable application a scratch coat to provide dimensional uniformity of the scratch coat.